Protective device



Dec. 11 1923. 1,477,304

C. T. ALLCUTT PROTECTIVE DEVICE Filed March '7, 1919 WITNESSES: INVENTOR Q. Chester T/l/lcuft 7 'ATTORNEY Patented Dec. 11, 1923.

UNITE STATES PATENT OFFICE.

CHESTER T. ALLCUTT, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO "WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION 01' PENNSYL- VANIA.

PROTECTIVE DEVICE.

7 Application filed March 7, 1919. Serial No. 281,165.

To all whom it may concern:

Be it known that I, CHESTER T. ALLCUTT, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Protective Devices, of which the following is a specification.

My invention relates to discharge gaps as used, for example, in lightning arresters, and it has for its object to provide apparatus of the character designated that shall op-' erate selectively. and permit current passage therethrough, preferably having a low current-impulse ratio, or, in other words, permitting the passage of high-frequency currents at equal or lower voltages than currents of normal frequency In the accompanying drawings, Figs. 1 to 4, inc1usive, are diagrammatic views illustrating' various forms of my invention, Fig. 4 showing the preferred construction.

In my former application, Serial No. 216,088, filed Feb. 8, 1918, I disclose apparatus functioning in this manner, an antenna being disposed between the main discharge electrodes and being connected thereto through-impedance devices of dissimilar character, the adjustment being such that, at normal frequency, the drops in said impedance devices determine the potential of this antenna at a value substantially the same as that of the immediately adjacent electrostatic field. Upon a change in the frequenc of the system, the drops in the two impe ance devices change t eir relative ratio so as to cause the antenna to assume a potential different from that which the main electrodes strive to set up in the field immediately adjacent to the antenna. Thus, the

antenna disturbs the electrostatic conditions with a change in the frequency and this effact may be so pronounced as to cause a given gap to break down with a high-frequency voltage far lower than the gap Wlll hold at normal frequency My present invention embodies a modification of the structure described in my previous application for a speclal type of service, that is, for use on direct-current apparatus.

It will be obvious that, although the apparatus described in my PIBVlOllS application could be used on direct-current ap aratus, the leakage of the condensers mg cially adapted for direct current apparatus A is desirable. Briefly, the present invention consists in replacing the devices specially adapted for alternating current by apparatus specially adapted for direct current.

Referrinq to Fig. 1 of the drawing for a more detailed understanding of my invention, I show a line wire 5 connected to a horn-shaped discharge member 6. A similarly shaped discharge member 7 is connected to ground at 8, either directly or through current-limiting devices, as may be desired. A small antenna 9 is mounted between the bases of the horns 6 and 7 and is connected to the horn 6 through a resistor 10 and a condensive reactor 11, and to the horn member 7 through a resistor 12. When the member 9 is disposed at the middle of the gap, the resistors 10 and 12 are of substantially equal value and serve to maintain the antenna 'at a potential midway between those of the horn members 6 and 7 The condenser 11 has a very small leakage and, therefore, when the frequency of the supply current in the line 5 is zero or direct current, the

condenser 11 will have no efi'ect upon the potential of the antenna 9. However, when a potential surge occurs on the line, due either to lightning or to a switching surge, the condenser will serve to raise the potential of the antenna member 9 to substantially that of the horn member 6, thus reducing the discharge gap to 50% of its former length, and, if the potential of the antenna 9 is raised high enough, a discharge will obtain between the discharge member 7 andv the antenna 9. resulting in ionization of the entire discharge gap and a breakdown from the discharge member 7 directly to the discharge member 6. The resistance member 10 will aid in establishing the discharge between the members 6 and 7 on account of the fact that it ofiers constant resistance to the current naming through the antenna 9.

It will, of course, be obvious that the antenna member 9 could be placed closer to the one or the other of the discharge members 6 and 7, instead of midway between them, the only essential feature being that the resistance members 10 and 12 shall have values proportional to the distances to therespective discharge members.

. In Fig. 2, I show a discharge gap in which nakrageoea resistor and a condenser connected in muitiple relation between said auxiliary electrode and the remainin discharge member.

8. In electrical-spar -discharge-gap apparatus, the combination with two discharge members mounted in spaced relation to each other and connected to a supply circuit, of an auxiliary electrode mounted intermediate said discharge members, and a circuit embodyingresistance and inductance connected between said auxiliary electrode and one of said discharge members, and means embodying resistance connected between said auxiliary electrode and the remaining discharge memberg-said circuits having impedances inversely proportional to the distances between the auxiliary electrode and the respective discharge members under normal operating conditions.

9. In electrical-spark-discharge-gap apparatus, the combination with two discharge members mounted in spaced relation to each other and connected to a supply circuit, of an auxiliary electrode mounted intermediate said discharge members, and a circuit embodying resistance and capacitance connected between said auxiliary electrode and one of said discharge members, and means embodying resistance connected between said auxiliary electrode and the remaining discharge member, said circuits having impedances inversely proportional to .the distances between the auxihary electrode and the respective discharge members under normal operating conditions.

10. In electricalspark-dischargegap apparatus, the combination with two discharge members mounted in spaced relation to each other and connected to a supply circuit, of an auxiliary electrode mounted intermediate said discharge members and a cir.

cuit embodying resistance and reactance connected between said auxiliary electrode and one of said discharge-gap members and a circuit embodying resistanceand capacitance connected between said auxiliary electrode and the remaining discharge gap member, said, circuits having impedances in versely proportional to the distances between the auxiliary electrode and the respective discharge members under normal operating conditions. 7 Y

i .11. The combination with an electricalspark-discharge-gap device comprising two spaced discharge members one of which is connected to a source of electromotive force and the other of which is connected to a circuit to which it is desired that the source of electromotive force be connected when the discharge gap breaks down, of an auxiliary electrode mounted. adjacent to said discharge members and conductively connected to both of said discharge members through impedance devices.

12. The combination with an electricalspark-discharge-gap device comprisi two spaced discharge members, one of whlch is connected to a source of electromotive force and the other of which is connected to a circuit to which it is desired that the source of electromotive force be connected whenthe dischar e gap breaks down, of an auxiliary elcctrod e mounted adjacent to said discharge members and conductively connected to both of said discharge members,,and.

means for causing the impedance between said auxiliary electrode and one of said main electrodes to change upon an alternating current being impressed upon said source of electromotive force.

In testimony whereof, I have hereunto subscribed my name this 19th day of Feb.,

CHESTER T. ALLCUTT. 

